In semiconductor vacuum processing, semiconductor slices are stored in cassettes formed from plastic or other suitable material. The plastic cassettes are then placed in a vacuum container, and the semiconductor slices are removed, often by robot arms, from the cassettes for various processing steps to form complete semiconductor devices. Over time, these cassettes can become warped from exposure to heat or damaged from handling. When damage to the cassette occurs, it becomes difficult to program an automatic robot arm to accurately locate and remove the slice from the cassette, as robot arms require exact alignment of the semiconductor slices. It is, therefore, desirable to ensure that the cassette is positioned so that the semiconductor slices are very accurately aligned. To achieve accurate positioning of a slice, it is necessary to force the cassette square, i.e., vertical surfaces vertical and horizontal surfaces horizontal, to remove the effects of any bending or warping that has occurred to the cassette.
In an attempt to properly position and hold the cassettes in a vacuum container, several unsatisfactory alternatives have heretofore been developed. One alternative involves the use of hydraulically or pneumatically activated clamp fingers which are used to grip the vertical sidewalls of the cassette and force them against the walls of the vacuum container in which they are positioned for use. The use of these fingers generally suffice to secure the cassette in place, but will not compensate for any warpage or bend in the cassette. Therefore, the semiconductor slices may not be accurately positioned in case of damage to the cassette.
Another alternative heretofore developed involves the use of a hydraulically or pneumatically activated cylinder having an attached push plate. When the cassette is placed in position in a vacuum, the hydraulic or pneumatic cylinder is activated to press the plate against the back of the cassette, forcing the cassette against the wall of the vacuum container. Again, this method will suffice to secure the cassette in place, but does not compensate for any warpage or bend in the cassette and the semiconductor slice may thus not be accurately positioned.
Other alternatives have been developed that will compensate for warpage or bend as well as secure the cassette in place. These methods are complex devices that include hydraulic or pneumatic cylinders that pass through the walls of the vacuum container. Any device that passes through the walls of the container will create an opening that must be sealed to keep the vacuum. These alternative methods have not provided a simple device that compensates for warpage or bend and still provides an effective seal. Thus, a need has arisen for a holding and clamping device that will properly position the cassette and compensate for any warpage or bend in the cassette so that the semiconductor slices are very accurately positioned for removal by an automatic robot arm or device and still maintain a vacuum within the container.